BODY IMPEDANCE MEASURING DEVICE

Description

[0001] Recently, the development of medical body impedance measuring devices has seen a trend away from measuring body compartments using whole-body impedance and towards measuring them using segmental impedance measurements. Whole-body impedance analysis considers the human or animal body as composed of various electrically conductive parts and attempts to account for the different diameters and lengths of these electrical conductors (namely arms, legs, and torso) using mathematical models. Since the resistance of an electrical conductor depends primarily on its length and cross-section, apart from its specific resistance, this method requires the assumption of fixed ratios between body size and the diameters and cross-sections of the torso and extremities. Standard proportions of the human body are typically used for this purpose.These models and assumptions, for example, originate from measurements taken on US Army personnel. However, these models and assumptions introduce such inaccuracies into the method that it is only approximately applicable to the examination of healthy individuals, but not to sick people.

[0002] Segmental impedance measurement of body compartments, especially when performed at multiple different frequencies, allows for a better consideration of the varying dimensions of body parts and their impact on AC conductivity. Segmental impedance measurement is particularly useful for differentiating between intracellular and extracellular water using multi-frequency measurements. Despite significant advances in this field, these methods have not yet been successfully integrated into routine bedside care. An exception is the measurement of lymphedema in individual extremities, or the attempt to quantify over- and underhydration in dialysis patients in a specific body part, namely the lower leg.

[0003] Numerous patents have been filed for segmental impedance analysis. For example, in the impedance measuring device proposed in WO 2007 / 002991 (Chetham) and US 8781551 (Chetham), the measuring current is measured and then adjusted; no switching options are provided. US 8594781 (Chetham) discloses an impedance measuring device in which measuring electrodes are switched off to eliminate inductive interference. In the impedance measuring device according to US 2011 / 0087129 (Chetham), a first system determines the impedance procedure and selects instructions; a second system generates control signals according to these instructions. Chatham in US 8548580 proposes two systems, the first of which selects the instructions for the measurement and transfers these instructions to a second system.Patent application US 2008 / 0009757 A1 (Tsoglin) discloses an impedance measuring device in which current distortions in unmeasured body sections are taken into account according to an electrical model, which is evidently Kirchhoff's rules. Cha in US 8386028 examines two segments simultaneously at two different frequencies. In US 2011 / 0046505 (Cornish), two different body segments are compared with each other.

[0004] WO 2008 / 031030 (Bartnik) discloses the determination of systolic time intervals by subtracting a second waveform, obtained from echocardiography, pulse wave, or pulse oximetry, from a first waveform derived from an impedance signal. WO 2006 / 063255A2 (Bernstein) discloses the determination of stroke volume from the impedance signal over the thorax or brachial artery. US 2013 / 0096448 (Brooks) describes a combined ECG (electrocardiography), ICG (impedance cardiography), and phono electrode on a common carrier with an acoustic chamber. Documents US 8521264 and US 2010 / 0324404 describe the use of a maximum of three combined ECG-ICG electrodes, all placed on the thorax. US 6339722 (Heethaar) proposes measuring the thorax as one segment at two frequencies and with two different measurement distances to obtain information about cardiac activity.

[0005] Documents WO2014 / 128237 A1, EP 1 731 092 A1 and US 6,321,112 B1 disclose further devices for measuring impedance on segments of a human or animal body.

[0006] For a quick and straightforward multi-segment multi-frequency impedance analysis, it is necessary to automatically and efficiently measure numerous body segments without user intervention. This is typically achieved using a multiplexer integrated into the device. Multiplexers for impedance measurement are sometimes used in the impedance meters mentioned above to apply current to different parts of the body and simultaneously measure the voltage at different locations.

[0007] However, this presents several difficulties not considered in the aforementioned documents. For many applications, the distance between the measuring instrument and the object under test must be kept large, resulting in relatively long cable lengths. This can cause significant difficulties and errors in the measurement. For example, parasitic capacitances and inductances can arise from the cables and their shielding. Investigations by the applicant have shown that, in particular, it is essential to prevent parasitic leakage currents from flowing into additional cables not intended for current supply at the time of application. Furthermore, it is crucial to prevent stray impedances and capacitances from distorting the measured signals in the individual cables due to the combined supply and measurement cables leading to numerous supply and measurement points.

[0008] The object of the present invention is therefore to create a device that avoids these difficulties and disadvantages of the prior art.

[0009] The present invention solves this problem by means of a device having the features of claim 1. Advantageous embodiments of the invention are set out in the dependent claims.

[0010] The device according to the invention for measuring the impedance of segments of a human or animal body, wherein the impedance measurement is preferably a multi-frequency impedance measurement, comprises a current source, current switches, current electrodes that can be arranged on segments of the human or animal body, and measuring electrodes. Each output of the current source is connected to an input of a current switch, wherein each current switch has a plurality of outputs and the input of the respective current switch can be switched to one of its outputs, the outputs of the current switches being connected to electrical supply lines of the current electrodes. The measuring electrodes detect voltage signals, and the device determines the impedances of the segments of the human or animal body from the current supplied by the current source and the detected voltage signals.Switching devices are installed in the supply lines near or directly adjacent to the current electrodes, allowing the current electrodes to be connected to and disconnected from their supply lines. The device is configured to connect only two current electrodes to the power source at a time by switching the current changeover switches and the switching devices, and to disconnect all remaining current electrodes from the supply line by switching the switching device, and to disconnect the supply line from the power source by switching the current changeover switches.

[0011] Preferably, voltage amplifiers or voltage followers with high input resistance are inserted into the signal lines close to or directly at the measuring electrodes.

[0012] For automatic measurement processes, the switching devices should be designed to be switchable by the device.

[0013] For the automatic measurement of impedances at different body segments, one embodiment of the invention provides that signal lines of the measuring electrodes are connected to inputs of voltage switches, each voltage switch having an output that can be connected to an input of the voltage switch. With this configuration, impedance measurement can be simplified by connecting the outputs of the voltage switches to inputs of a differential amplifier, which determines a differential voltage from the voltage signals applied to its inputs. This differential voltage is then used by the device for impedance determination.

[0014] High reliability and fast measurements are achieved by designing the current switches and / or the voltage switches as relays or multiplexers.

[0015] A significant improvement in measurement results is achieved when the device according to the invention is equipped with common-mode rejection. For this purpose, the invention provides that at least one of the current electrodes can be supplied with a balancing current via a resistor, the connection of the resistor to the current electrode being arranged between the switching device and the current electrode. Alternatively or additionally, a balancing current electrode is provided which can be supplied with a balancing current via a resistor.

[0016] The handling of the device according to the invention is particularly easy for the examination personnel if, apart from any individual measuring electrodes that may be present, a current electrode and a measuring electrode are grouped together to form a single electrode region. Handling of the device is further simplified by having the current electrode and the measuring electrode of the single electrode region share common cables for power supply and signal transmission, since this measure reduces the number of cables that need to be handled. Handling is further simplified by arranging the current electrode and the measuring electrode on a common electrode carrier. The common electrode carrier is preferably a clamp, a band, a cuff, or a pressure cuff (similar to those used for blood pressure measurement).When a clamp, cuff, or pressure cuff is used, a pressure sensor for pulse measurement can also be attached to it. For automatic measurements, it is advantageous if the pressure sensor has a fluid-filled bladder that communicates with a pressure transducer, preferably being pressed against a body part by means of a controlled, hydraulic, or electric motor-driven pressure device.

[0017] It has been shown that the accuracy of the measurements is significantly increased when the device connects the current electrode to the current source from a maximum of one combined electrode region and uses the measuring electrode for voltage measurement. In this respect, it has proven advantageous if combined electrode regions can be selected for placement on peripheral and central body segments, and optionally, a further combined electrode region can be selected for placement on a body region where the chest electrodes V1 to V6, preferably V4 to V6, of an ECG are located. In the simplest application, however, only one of the chest electrodes V1-V6, preferably V4 to V6, needs to be used as the measuring electrode for impedance measurement.

[0018] Furthermore, it is advantageous if the device is equipped with a differentiator for determining the change in impedance with the heartbeat.

[0019] In a preferred embodiment of the device according to the invention, an ECG device is integrated into the device, wherein the ECG device has at least extremity electrodes, and preferably also chest wall electrodes. This makes it possible to perform impedance measurements and ECG recordings simultaneously with the device according to the invention. To minimize the number of electrodes to be attached to the body, the invention also proposes that the measuring electrodes be designed as ECG electrodes by routing branch lines of the signal lines of the measuring electrodes to the ECG device.

[0020] If the current electrodes and / or the measuring electrodes are designed as sensors and / or transmitters for physical quantities, in particular acceleration values, pressure, sound, temperature, or light, other physical quantities and parameters can also be measured during impedance measurements. Measurement reliability and ease of use are achieved by designing at least some of the current electrodes and the measuring electrodes as suction electrodes or adhesive electrodes.

[0021] The invention is explained in more detail below with reference to exemplary embodiments and the drawings. Fig. 1 shows a schematic block diagram of the device according to the invention. Fig. 2 shows application examples of the device according to the invention.

[0022] The following description refers to Fig. 1 and Fig. 2 Reference is made. In each of the two figures, identical parts with an identical configuration are shown multiple times side by side for the sake of clarity, each marked with a reference symbol only once.

[0023] Fig. 1 Figure 1 shows a schematic block diagram of the device 2 according to the invention for measuring the impedances of segments of a human or animal body. The device 2 comprises a current source 4 with two partial current sources 4a, 4c of opposite polarity, which are controllable by a control current Isoll. The control current Isoll passes through an inverter 4b before entering one of the partial current sources 4c. The output of each partial current source 4a, 4c is connected to the input of a current switch 3, which is, for example, implemented as a multiplexer. Each current switch 3 has a plurality of outputs, with the input being switchably connected to one of the outputs. The outputs of the current switches 3 are connected to current electrodes 8 by means of electrical supply lines 5. The current electrodes 8 are shown with dotted areas.The current electrodes 8 are applied to individual body segments of the organism under investigation (human or animal). The surface of the organism under investigation 6 is symbolically represented in the figure by a dashed outline. Switching devices 7 are integrated into the supply lines 5 near the current electrodes 8, allowing the current electrodes 8 to be switched on and off from the supply line 5. This prevents parasitic leakage currents from the current electrodes 8 from reaching the device 2 during operation, as the switching devices 7 disconnect the current electrodes 8 from the supply lines 5 when switched off. The switching devices 7 can be designed as mechanical switches (e.g., microrelays), electronic switches, or negative impedance converters.Thus, each supply line 5 is switched off from the power source 4 in the device 2 by the current switch 3 and, additionally, a second time from the current electrode 8 by the switching device 7 peripherally to the device 2. This prevents parasitic leakage currents that could enter the supply line cables 5 from the periphery via the organism's body. This is particularly important because the supply line cables 5 should be advantageously shielded and—for even better shielding—provided with active shielding. However, this could also allow alternating current generated via capacitances between the cable and the shield to flow, which is prevented by the switching devices 7.

[0024] In the exemplary embodiment of Fig. 1 Six current electrodes 8 are provided. The first four current electrodes 8 are examples of current application at the right leg (designated RL C for right leg current), the left leg (designated LL C for left leg current), the right arm (designated RA C for right arm current), and the left arm (designated LA C for left arm current). The fifth, optional current electrode 8 is intended for application at the upper thoracic aperture, e.g., near the upper sternum, at the neck, or at the head (designated NC for neck current). The sixth current electrode 8 is intended for current application at the lower end of the thorax (designated Th C), e.g., in the region where leads V4 to V6 or V4r to V6r are arranged for an ECG.

[0025] Each current electrode 8 is associated with a measuring electrode 14, wherein the current electrode 8 and the measuring electrode 14 are not electrically connected to each other and the combination of current electrode 8 and measuring electrode 14 is arranged on the organism 6 in a so-called combined electrode region 1. The distance between the electrodes 8 and 14 of the combined electrode region should be at least 2 cm to 4 cm, preferably 3 cm to 4 cm, and at most 20 cm to 30 cm. In the exemplary embodiment of Fig. 1 For example, there are six combined electrode regions 1, each with a current electrode 8 and a measuring electrode 14, as well as at least one additional measuring electrode 20.

[0026] The measuring electrodes 14 are designated RL V for right leg voltage, LL V for left leg voltage, RA V for right arm voltage, LA V for left arm voltage, NC for neck voltage, and Th V for thorax voltage. Each measuring electrode 14 can be arranged together with the associated current electrode 8 on a suitable common electrode carrier, such as a clamp electrode, adhesive electrode, suction electrode, band electrode, cuff electrode, or pressure cuff electrode. Alternatively, the measuring electrodes 14 and current electrodes 8 are provided as separate individual electrodes.

[0027] The measuring electrodes 14 are connected to signal lines 19, which lead to the inputs of two voltage switches 10. Voltage amplifiers 9 are connected in the signal lines 19. The voltage amplifiers 9 can be implemented as voltage followers with high input impedance. The voltage amplifiers 9 should be arranged as close as possible to, or directly adjacent to, the measuring electrodes 14. The voltage switches 10 are implemented, for example, as relays or electronic voltage multiplexers. A signal from each measuring electrode 14 can be switched to the outputs of the voltage switches 10 by means of the voltage switches 10, where it is then routed for further processing, e.g., to an input of a differential amplifier 11. The output signal UDiff of the differential amplifier is the difference between the output signals of the two voltage switches 10.

[0028] Another important prerequisite for the optimal functioning of the device 2 is the provision of common-mode rejection, as there is significant electromagnetic interference from the organism 6 under investigation. Alternating current interference caused by the power supply network can also cause considerable disturbances. Furthermore, the mismatch between the different cable capacitances and impedances of the supply lines 5 and signal lines 19 must be compensated for. In addition to the usual methods of optimal cable shielding, including the use of active shielding and special signal filter techniques such as adaptive filters or notch filters, common-mode voltage compensation is necessary. This is achieved by driving a compensating current through a high resistor 12 with a resistance value between 470 kΩ and 1.5 MΩ, preferably 1 MΩ.For this to work, one terminal of resistor 12 must be connected to at least one of the supply lines 5 to the current electrodes 8, specifically between the switching device 7 and the current electrode 8. The other terminal of resistor 12 is connected to the output of an operational amplifier 13, which supplies the balancing current. Advantageously, resistor 12 is placed close to the current electrode 8 used for supplying the balancing current. Each of the current electrodes 8 is suitable for supplying the balancing current. Alternatively or additionally, a dedicated balancing current electrode 8a can be provided, which is connected via a resistor 12a (between 470 kΩ and 1.5 MΩ, preferably 1 MΩ) to the output of an operational amplifier 13a, which provides the balancing current in a known manner.

[0029] With the device 2 constructed in this manner, many segments of the organism 6 can be automatically examined in detail. On the one hand, it is possible to generate alternating currents of any frequency using the control signal Isoll and the two inverted partial current sources 4a, 4c, and to direct these currents to freely selectable current electrodes 8 by means of the two current switches 3. On the other hand, voltage signals from freely selectable measuring electrodes 14 can be selected for further processing, in particular for differential calculation at the differential amplifier 11, using the two voltage switches 10. The control of the control signal Isoll, the current switch 3, the voltage switch 10, the mathematical processing of the voltage signals determined by the measuring electrodes 14, as well as the control of all other functions of the device, is carried out by means of a CPU 23 built into the device 2, which is implemented, for example, in the form of a microcontroller.The numerous necessary connections to CPU 23 are not shown for the sake of clarity.

[0030] Thus, it is possible to automatically perform impedance measurements at different frequencies on different segments of the organism 6 using the device 2. Based on these impedance measurements on different body segments, the device 2 also offers the possibility of impedance cardiography (ICG).

[0031] Furthermore, the CPU 23 in the device 2 can, based on impedance measurements, calculate the body composition of the organism 6 and its body parts, such as the body water contained in body parts, the extracellular fluid, the muscle mass, the fat mass, their deviations from the target value, as well as edema or fluid accumulation in body parts, using stored empirical equations or predefined mathematical models. The calculated results can be displayed on a screen, stored in non-volatile memory, or processed further in databases. It should be emphasized that the physician can use the device 2 to diagnose deviations in hydration from the norm, e.g., deviations in the ratio between fat mass or "lean body mass" to extracellular volume or in the ratio of extracellular to intracellular volume.Whole-body water volume measurements can be performed, thus enabling better detection of overhydration or dehydration. Furthermore, arterial circulatory disorders, especially in the legs or their segments, can be detected and displayed. For example, the difference in the acceleration of leg volume with the heartbeat can be used to calculate an "Ankle Brachial Index" (ABI), as described in the literature. The impedances determined by device 2, along with their resistive and reactive components and the phase angle of the impedance, are used to develop regression equations via multiple regressions or neural networks. These equations help to estimate the parameters of interest to the physician and predict parameters determined using gold standard methods such as whole-body DXA, deuterium dilution, sodium bromide dilution, or other tracers.

[0032] If the device 2 further differentiates the determined impedance signals and relates them to the heartbeat, the resulting calculated change in impedance with the heartbeat can be used to measure the acceleration of blood in different parts of the body. This is particularly useful when performed in a segment defined by a central combined electrode region (e.g., located on the neck, nape, or shoulders) and another central single electrode (selected, for example, from V4 to V6 or from V4r to V6r) and a peripheral combined electrode region, as well as a central and a peripheral combined electrode region, as described in Skrabal et al., Medical Engineering & Physics 36 (2014) 896-904. The only essential requirement is that at least one measuring electrode 14 is positioned between two current electrodes 8.This allows not only for the assessment of cardiac function and the diagnosis of heart failure, but also, in the context of impedance rheography, the measurement of arterial and venous blood flow, as well as pulse wave transit time (volume wave transit time). Here, too, gold-standard procedures such as echocardiography and other hemodynamic methods like the ankle-brachial index, pulse wave transit time, pulse wave analysis with augmentation index, central and peripheral compliance, and stroke volume from the pulse waveform are advantageously used as gold-standard procedures to calibrate the new methods.

[0033] The device 2 can also integrate an ECG device 21. This ECG device 21 can be equipped with its own ECG electrodes, which, for the sake of clarity, are located in Fig. 1 not shown. However, a particular advantage of the device 2 is the possibility of implementing the measuring electrodes 14 as ECG electrodes by connecting branch lines 22 from the signal lines 19 of the measuring electrodes 14 to the ECG device 21, preferably between the voltage amplifier 9 and the voltage switch 10. This allows the device 2 to function as a multi-channel ECG device and simultaneously perform the described impedance measurements and calculations from the determined impedances while recording a multi-channel ECG. Since recording over a period of time, e.g., 2 to 3 minutes, is advantageous for obtaining the templates, a rhythm strip is automatically generated, as is desired and customary for a standard ECG. This also enables a spectral analysis of the heart intervals and the changes in impedance with the heartbeat.This allows the corresponding frequency bands, such as the 0.1 Hz and 0.3 Hz bands, to be used to determine the contributions of the sympathetic and vagal nervous systems to heart rate regulation. This is particularly useful for identifying overtraining, burnout, depression, etc., especially when the changes can be tracked over weeks and months. All of this requires no additional time compared to a standard ECG rhythm strip.

[0034] The invention also provides that sensors or actuators, such as accelerometers, pressure sensors, light sensors, LEDs, or pressure pumps, are attached to the current electrodes 8 or measuring electrodes 14. Fig. 1 A sensor / transmitter 17 is schematically depicted lying directly beneath an electrode (either a current or measuring electrode can be used). Optionally, it can also be configured as a sensor and / or transmitter 17a located next to the electrode. The sensor 7 and / or transmitter 17, 17a is controlled by an evaluation unit 18, which in this case also acts as a generator for the measured quantity to be input, e.g., a pressure signal. The sensor / transmitter 17, 17a is connected to an input of the evaluation unit 18, which evaluates the acquired measured quantity, e.g., a pressure signal, acceleration signal, temperature signal, etc. With such sensors, the device 2 can simultaneously measure impedance and record ECGs, as well as other circulatory parameters such as circulation times, pulse wave analysis including stroke volume, pulse oximetry, etc.Pulse wave analysis can be performed using methods detailed in WO 2004 / 030535 A1 (Skrabal) and EP 2319411 A2. It can also be used to calculate other parameters such as arterial stiffness, augmentation index, central aortic pressure, sleep volume, etc. The possible application of blood pressure cuffs, including on the lower extremities, for determining the ankle-brachial index and for venous occlusion plethysmography is also possible.

[0035] Thus, device 2 represents a measuring device which, in its fully developed state, not only performs impedance measurements on multiple body segments of a human or animal body at several or numerous impedance frequencies, but also optionally includes a differentiator (which can be integrated into CPU 23) for detecting the impedance change with the heartbeat. The heartbeat can be precisely identified from the ECG, allowing a time window to be defined for searching for the impedance change with the heartbeat. Templates are generated from the various segments for impedance cardiography and impedance rheography. The measuring device is therefore also potentially a (multi-channel) ECG device and serves as an analyzer for other physical quantities, provided the corresponding sensors and actuators are integrated into the electrodes.

[0036] Fig. 2 This figure illustrates, using four examples A, B, C, and D, the application of the principle of partial or complete separation of the combined electrode regions 1 for current input (C) via the current electrodes 8 and voltage measurement (V) via the measuring electrodes 14 of the device 2. As can be seen, in these examples, the combined electrode regions 1 for current input on the one hand and voltage measurement on the other are used partially or completely differently. The current electrodes are shown here with dotted areas, the measuring electrodes in white. If an electrode pair is anatomically located outside the circuit, it is also displaced in the drawing and shown outside the circuit.

[0037] In one embodiment of the invention, the device determines the impedance and a change in impedance with the heartbeat in at least two body segments, wherein the segments are defined as follows. a) On the one hand, the central segment with respect to the current input is defined by the current electrodes 8 of a central (Z) combined electrode region 1 and a peripheral (P) combined electrode region 1; on the other hand, the measuring section is defined by the measuring electrode 14 of the central combined electrode region 1 and by a measuring electrode 20, which is also used for recording the chest wall ECG. Fig. 2-A (Solid measuring section V.) Here, a further central combined electrode region 1 could be used, though less conveniently, with its measuring electrode 14 used to measure the impedance and its current electrode 8 used to supply the current (not shown). Alternatively, with the same supply as above, the measuring section V could be defined by the measuring electrode 14 of the central combined electrode region and by the measuring electrode 14 of a combined electrode region that is not within the circuit (e.g., positioned on the contralateral leg). (See dashed measuring section in Fig. 2 A .) b) On the other hand, the peripheral body segment in the current injection is defined by the current electrodes 8 of two peripheral combined electrode regions (e.g. attached to both legs), while the measuring section is defined by a measuring electrode that lies outside the circuit (e.g. the ECG electrode 20 located over the chest wall) and the measuring electrode 14 of the combined electrode region 1, which was also used for current injection ( Fig. 2-B , continuous measuring circuit). Alternatively, with the same power supply, the measuring circuit could be defined by a measuring electrode 14 located outside this circuit of a central combined electrode region and by the measuring electrode 14 of the electrode region used for power supply ( Fig. 2-B , dashed measuring section). Analogously, another segment between the central single electrode 20, which could correspond to an ECG chest electrode, and the measuring electrode 14 of a combined electrode region that is not carrying current can also be analyzed (dashed line with V'). This could, for example, be the abdominal segment. c) Fig. 2-C shows a similar measurement setup as Fig. 2-B , with which another peripheral body segment can be measured. This could, for example, be the arms. This figure illustrates how many different measuring points can be used, as long as they are located outside the circuit. This also applies to the other figures 2-A, 2-B, and 2-C, although this is not shown there for the sake of clarity. However, the current should be applied in such a way that two body segments with pulsatile volume changes are not simultaneously subjected to electrical current and measured, because the pulsatile components would mix. It would then be possible, but tedious, to calculate the pulsatile components of the two sections separately. d) Fig. 2-D Figure 1 shows a measuring arrangement with which partial segments of a peripheral body segment can also be measured if additional individual measuring electrodes 14a are attached between peripheral and central electrode pairs. The depicted measuring segment V serves to measure the entire segment, the depicted measuring segment V' serves to measure the proximal part, and the segment with the hatched line serves to measure the peripheral body segment.

[0038] In all representations in Fig 2 In accordance with the invention, alternatively only one measuring section is always enabled by the voltage switch 10, and the power supply is advantageously always only in the segment that is currently being examined; all other segments are switched off by the additional switching devices 7 and the current switch 3.

[0039] Thus, with a minimum of current switching, any body segment can be measured with respect to both its impedance and its change in impedance with the heartbeat. It is also obvious to any person skilled in the art that only a fraction of the possible alternatives offered by this switching system are shown, and its application is not limited to the current and voltage circuits depicted in the drawings.

[0040] The essential feature of the impedance measurements of the device 2 is that, among all combined electrode regions 1, only one combined electrode region uses both the current electrode 8 for current injection and the measuring electrode 14 for voltage measurement. In all other combined electrode regions, either only one of the two electrodes 8, 14 is used, or neither electrode 8, 14 is used at all.

[0041] Regarding the design of electrodes 8 and 14, it is advantageous for handling if at least some of them are designed as suction electrodes, clamp electrodes, adhesive electrodes, band electrodes, cuff electrodes, or pressure cuff electrodes. These can be configured as spot electrodes, band electrodes, or double-band electrodes, with double-band electrodes being advantageously positioned at different angles to each other rather than parallel. The electrodes, especially the adhesive electrodes, which are typically disposable, can also be used for identification, for example, via RFID or other methods. This ensures the accuracy of the measurement results by allowing the use of only those electrodes with which the device was originally calibrated, thus guaranteeing the necessary quality and configuration.

[0042] In summary, the device 2 according to the invention enables impedance measurement of body segments at several frequencies, if expedient also using a Cole-Cole plot, for the determination of intracellular water (or muscle mass and fat mass) as well as extracellular water. Furthermore, it enables impedance measurement by dividing the body into its various segments, e.g., arms and legs (or even just segments of the arms and legs), into the torso and its parts, namely the thorax and abdomen (since these have very different compositions and thus different specific resistances). This is possible using as few feed lines 5 to the body as possible and as few electrodes 8, 14 on the body of the organism 6 as possible. The present device 2 can employ the so-called 4-point method with current electrodes 8 located externally or in close proximity and measuring electrodes 14 located internally or in close proximity.

[0043] The combined electrode regions 1 are designed for placement on different parts of the body, so that a distinction can be made between peripheral electrode regions (at the ends of the extremities of living bodies) and central electrode regions (located on the trunk, neck, head area).

[0044] Peripheral united electrode regions are applied to: a) Fingers, hands, forearms for current injection and voltage measurement (e.g., injection of current from fingers, hand, or hand and forearm for voltage measurement on the left and right upper extremities). b) Toes, feet, lower legs for current injection or feet and lower legs for voltage measurement on the left and right lower extremities.

[0045] Central combined electrode regions are applied to: c) Head, neck, upper chest for current injection and / or voltage measurement. In this area, a single electrode may suffice for voltage measurement. d) Lower chest for current injection and voltage measurement; in this area, electrodes for voltage measurement alone may suffice.

[0046] Other regions of the body that can be subjected to a similar measurement approach, e.g., localized body regions such as parts of the skull, neck, chest, abdomen, or breast, can also be selected for the placement of combined electrode regions.

[0047] The above descriptions clearly demonstrate the complexity and multifaceted design and operation of device 2. Therefore, the implementation of the current switch 3 and voltage switch 10 as multiplexers has proven effective. The use of an FPGA for the circuit design also significantly simplifies the design. To integrate a multi-channel ECG into the measurements, the CPU 23 must possess substantial processing power and therefore be a high-speed processor, while the data storage must also be sufficiently large and fast. A large screen should be available to display the numerous synchronized data points and curves for visualizing the measurement results. Interfaces to existing medical systems can also be provided. The data should be made available for scientific analysis in suitable data formats, such as Excel, or other database formats.A data storage system has proven very effective, allowing for the numerical and / or graphical recording and display of changes in body composition, bodily functions, and ECG patterns for individual patients over time. This enables the use of empirical formulas, derived from gold-standard procedures (such as echocardiography, biochemical parameters like NT-proBNP or its derivatives, or other biochemical parameters that change in heart failure, ergometry, spiroergometry, oxygen uptake thresholds, lactate measurement, ankle-brachial index, arteriography, whole-body DXA, and deuterium and sodium bromide determination), to assess bodily functions and composition, such as...Cardiac output, cardiac fiber elongation, maximum performance, their threshold values, arterial and venous blood flow, muscle mass, fat mass, total body water, extracellular space, and their deviations from the norm are calibrated by estimating the above parameters, for example, using multiple regression equations, which may include anthropometric data as well as all impedance data, based on gold standard methods. To detect over- or underhydration or sarcopenia, calculating the deviation of TBW or ECW or ICW or ECW / ICW ratio from the regression line determined between FM / kg body weight on the one hand and TBW / kg body weight or ECW / kg body weight or ECW / ICW in healthy individuals on the other has proven particularly useful.For determining sarcopenia, the output of the "appendicular muscle mass," as defined internationally, has proven particularly useful. This refers to the muscle mass of the shoulders and arms on the one hand, and of the hips and legs on the other, and can be excellently measured using segmental impedance spectroscopy. Correcting the calculated muscle mass by adjusting for any potentially distorted ratio (e.g., quotient) between extracellular space and intracellular space or whole body water has also proven effective. This allows for the determination of the presence and grading of sarcopenia in comparison to a normal population.

[0048] The output and / or graphical representation of the time course of the determined parameters is particularly interesting, not only after individual interventions such as ergometry, pacemaker adjustments, pharmacological and physiological interventions, and not only for a single examination, but especially for repeated examinations at longer intervals. Here, for example, only time courses can be automatically selected in which the measured or calculated parameters have changed significantly and clinically relevantly since the last recording.Clinically relevant changes include, for example, changes in parameters that deviate from the known normal range, such as the PQ interval (indicating the development of an AV block), the QT duration above or below the rate-adapted normal range, ST depression or elevation above the known normal range, changes in the heart vector, the amplitude and direction of the T wave, sudden changes in heart rate, sympathovicarial balance, calculated power of the 0.1 and 0.3 Hz bands, or heart rate variability from the ratio of the 0.1 and 0.3 Hz bands, sudden differences occurring between segments, the volume wave in the legs, or increases in the ECF / ICF or ECF / TBW ratios in individual body segments, etc. This prevents confusing trend printouts.

Claims

1. Device (2) for impedance measurements on segments of a human or animal body, the impedance measurements preferably being a multi-frequency impedance measurements, wherein the device (2) comprises a current source (4), current changeover switches (3), current electrodes (8) placeable on segments of the human or animal body (6), voltage changeover switches (10) and measuring electrodes (14), wherein each output of the current source (4) is connected to an input of a current changeover switch (3), wherein each current changeover switch (3) has a plurality of outputs and the input of the respective current changeover switch (3) is switchably interconnectable with one of its outputs, wherein the outputs of the current changeover switches (3) are connected to electric feed lines (5) of the current electrodes (8), wherein the measuring electrodes (14) detect voltage signals and the device (2) determines the impedances of the segments of the human or animal body (6) from the current supplied by the current source (4) and the detected voltage signals, wherein switching devices (7) are incorporated into the feed lines (5) near or directly at the current electrodes (8), with which switching devices (7) the current electrodes (8) may be connected to or disconnected from their feed lines (5), wherein the device (2) is configured to always open up only one measuring section via the voltage changeover switch (10) and respectively connect only two current electrodes (8) to the current source (4) by switching the current changeover switches (3) and the switching devices (7), and to disconnect all other current electrodes (8) from the feed line (5) by switching the switching device (7), and to disconnect the feed line (5) from the current source (4) by switching the current changeover switches (3) wherein signal lines (19) of the measuring electrodes (14) are connected to inputs of voltage switches (10).

2. Device according to claim 1, characterized in that voltage amplifiers (9) or voltage followers with a high input resistance (9) are integrated into the signal lines (19) near or directly at the measuring electrodes (14).

3. Device according to claim 1 or 2, characterized in that the switching devices (7) are switchable by the device (2).

4. Device according to one of the claims 1 to 3, characterized in that the voltage changeover switches (10) each have an output that is interconnectable with an input of the voltage changeover switch (10).

5. Device according to claim 4, characterized in that the outputs of the voltage changeover switches (10) are connected to inputs of a differential amplifier (11), which, based on the voltage signals applied to its inputs, determines a differential voltage (Udiff), which the device (2) uses for the determination of impedance.

6. Device according to one of the preceding claims, characterized in that a compensating current may be applied to at least one of the current electrodes (8) or an additional electrode (8a) via a resistor (12), wherein the connection of the resistor (12) to the current electrode (8) is positioned between the switching device (7) and the current electrode (8).

7. Device according to one of the preceding claims, characterized in that a compensating current electrode (8a) is provided, to which a compensating current may be applied via a resistor (12a).

8. Device according to one of the preceding claims, characterized in that one current electrode (8) and one measuring electrode (14), respectively, are arranged on a common electrode carrier grouped into a combined electrode region (1), wherein current feeding always takes place with two current electrodes (8) that are respectively grouped in a combined electrode region (1), wherein, however, not more than one measuring electrode (14) is used at a time, which is positioned on one of the two combined electrode regions (1).

9. Device according to claim 8, characterized in that the device (2) interconnects the current electrode (8) of no more than one combined electrode region (1) with the current source (4) and uses the measuring electrode (14) for voltage measurements.

10. Device according to one of the claims 8 or 9, characterized in that combined electrode regions (1) are selectable for attachment to peripheral body segments and central body segments, wherein preferably a further combined electrode region (1) is selectable for attachment to a body region where the chest wall electrodes V1 to V6, preferably V4 to V6, of an ECG are placed.

11. Device according to any of the preceding claims, characterized in that a pressure sensor for pulse measurement is arranged on the common electrode carrier, in particular a liquid-filled balloon communicating with a pressure transducer, wherein the liquid-filled balloon is pressable against a body part, advantageously by means of a controlled, hydraulic- or electric motor-driven pressing device.

12. Device according to one of the preceding claims, characterized in that it determines the impedance and impedance changes with the heartbeat of at least two body segments, the segments being defined a) on the one hand, with regard to feeding by two combined electrode regions (1) positionable on a central (Z) body part and a peripheral (P) body part, and with regard to voltage measurements by a combined electrode region (1) positionable on a central (Z) body part and a centrally positioned single electrode (20); b) on the other hand, regarding current feeding by two electrode regions (1) positionable on peripheral (P) body parts, and with regard to voltage measurements by the peripheral (P) combined electrode region (1) and a central measuring electrode, either as single electrode (20) or as measuring electrode (14) of a central (Z) combined electrode region; wherein c) alternatively to b), the second body segment is also defined with regard to current feeding by a central (Z) and a peripheral combined electrode region (1), and with regard to voltage measurements by two peripheral (P) combined electrode regions, one of which does not carry any current.

13. Device according to one of the preceding claims, characterized in that an ECG device (21) is integrated into the device (2), wherein the ECG device (21) has at least extremities electrodes, preferably also chest wall electrodes.

14. Device according to claim 13, characterized in that the measuring electrodes (14) are implemented as ECG electrodes by providing branch lines (22) of the signal lines (19) of the measuring electrodes (14) to the ECG device (21).

15. Device according to one of the preceding claims, characterized in that the current electrodes (8) and / or the measuring electrodes (14) are implemented as transducers / generators (17, 17a) for acceleration values.

16. Device according to one of the preceding claims, characterized in that it has a CPU (23) that, by means of multiple regression equations or mathematical models, determines parameters of body functions and compositions, such as cardiac performance, biochemical parameters thereof, for the physical maximum performance, for the aerobic and anaerobic thresholds, for the circulation of body parts, for arterial and venous functions, e.g. the ankle brachial index, arterial and venous thromboses or arterial embolisms, the body compartments, whole-body water, extracellular space, muscle mass, fat mass, ratio between extracellular space and intracellular space or total-body water in the whole body and in individual body parts and their deviations from the norm.